The present invention relates to multi-layer products, and an apparatus and method for the injection molding of same. More specifically, it relates to a four-layer bottle preform and closure, and an apparatus and method for injection molding of same.
Multi-cavity injection molding apparatus for making multi-layer molded products, such as protective containers for food, preforms for beverage bottles, and closures, are well-known. One or more layers of one material are typically molded within, or together with, one or more layers of another material, to form the molded product. At least one of these layers is usually a barrier layer formed from a barrier material to protect the contents of the molded product. Since the barrier material is expensive, typically only a very thin barrier layer is used in the molded product. It is also generally desirable to have this thin barrier layer uniformly and evenly distributed (i.e., well-balanced) throughout the molded product to provide the proper protection for the contents of the molded product.
An example of an injection molding apparatus used to make four-layer preforms with thin barrier layers is disclosed in U.S. Pat. No. 4,990,301 to Krishnakumar et al. Krishnakumar et al. disclose an injection molding device having multiple and selective melt inlets, passages, channels, and gates, requiring different manifold configurations, for forming multiple layer preforms. In particular, Krishnakumar et al. disclose the use of one large central melt passage and three small annular melt passages flowing into a central channel that opens into a cavity for multi-layer preforms. Depending on the application, either the large central melt passage or one of the three small annular melt passages may be chosen for a barrier material. Krishnakumar et al. inject the barrier material from a selected passage into the cavity, either directly against a cooled portion of preform material previously disposed in the cavity, or after injecting a hot portion of preform material from another passage, in addition to the cooled portion, into the cavity.
There are several problems with the device disclosed by Krishnakumar et al. First, the injection molding device disclosed by Krishnakumar et al. uses multiple melt inlets, passages, channels, and gates that require several different configurations for the same manifold, depending on the application, to make multi-layer preforms. As a result, the injection molding device of Krishnakumar et al. is complex and expensive to both manufacture and operate. Second, injecting a barrier material directly against a cooled portion of preform material previously disposed in a cavity often results in an uneven, or interrupted, barrier layer that does not properly protect the contents of the molded preform. An altered and non-uniform barrier layer may also present problems with blowing out the preform. Third, injecting a barrier material only after injecting a hot portion of preform material, in addition to the cooled portion, into a cavity adds additional time to the injection cycle or production time for the preforms.
Finally, the injection molding device disclosed by Krishnakumar et al. uses large and small passages for the flow of barrier material. The large passage can be problematic, since it can retain too much barrier material at a high temperature, thereby causing the degradation of the barrier material. On the other hand, the small passages can cause high pressure drops for the barrier material as it enters the cavity, thereby damaging or washing out the preform material already in the cavity.
Another example of an injection molding apparatus used to make four-layer preforms with thin barrier layers is disclosed in U.S. Pat. No. 5,141,695 to Nakamura. Like Krishnakumar et al., Nakamura discloses a method to produce a three material, four layer preform, where preform material is injected first through an annular melt channel, and barrier layer is injected later from a separate annular melt channel simultaneously with a mixture of preform and barrier material injected through a central melt channel. Besides using multiple annular melt channels, which add to the complexity and expense of the injection molding apparatus, the method disclosed by Nakamura positions the thin barrier layer directly against the cooled portion of preform material already in the cavity. As previously explained, this arrangement results in an uneven, non-uniform, and unbalanced barrier layer within the preform. In addition, the small annular melt channel for the barrier material used in Nakamura""s method causes a high pressure drop as the barrier material enters the cavity, thereby potentially causing damage to the preform material already in the cavity.
Accordingly, it would be desirable to have an apparatus and method for injection molding of four-layer preforms or closures that overcomes the problems associated with the prior art by not having multiple melt inlets, passages, channels, and gates, and by having a single configuration for each of its manifolds. An injection molding apparatus and method for injection molding of four-layer preforms or closures without multiple melt inlets, passages, channels, and gates would be relatively simpler and less expensive, both to manufacture and operate.
It would also be desirable to have an apparatus and method for injection molding of four-layer preforms or closures that does not inject a barrier material either directly against a cooled portion of one preform material previously disposed in a cavity, or after injecting a hot portion of another preform material, in addition to the cooled portion, into the cavity. Such an apparatus and method would provide four-layer preforms or closures with more evenly and uniformly distributed barrier layers, and thus, better protection for the contents of the preforms or closures, without increasing the cycle or production time for the preforms or closures. Moreover, it would also be desirable to have an apparatus and method for injection molding of four-layer preforms or closures that avoids the problems associated with large and/or small passages or channel for barrier material.
The present invention provides an injection molding apparatus for multi-layer molding comprising a central melt channel and an annular melt channel radially spaced from the central melt channel. The apparatus also comprises a first melt passage in communication with the annular melt channel, a second melt passage in communication with the central melt channel, and a third melt passage in communication with the central melt channel.
In addition, the present invention provides an injection molding apparatus for multi-layer molding that comprises a central melt channel having a first portion for flow of a first material, a second portion for flow of the first material and a second material, and a flow extension connecting the first portion and the second portion. The flow extension also has a flow opening. The apparatus further comprises an annular ring channel surrounding the central melt channel for flow of the second material. The annular ring channel is also in communication with the flow opening of the flow extension. The apparatus also comprises an annular melt channel radially spaced from the central melt channel for flow of a third material.
Moreover, the present invention also provides an injection molding apparatus for multi-layer molding comprising a central melt channel for flow of a first material and a second material, and an annular melt channel radially spaced from the central melt channel for flow of a third material. The apparatus also comprises a cavity for receiving flow of the first material and the second material from the central melt channel, and for receiving flow of the third material from the annular melt channel.
The present invention also provides a method for injection molding of multi-layer products comprising the step of injecting afirst material from a first melt passage into an annular melt channel radially spaced from a central melt channel. The method also comprises the step of injecting a second material from a second melt passage into the central melt channel. In addition, the method comprises the step of injecting a third material from a third melt passage into the central melt channel.
Furthermore, the present invention provides a method for injection molding of multi-layer products comprising the steps of injecting a first material into a central melt channel having a first portion, a second portion, and a flow extension connecting the first and second portions, and injecting a second material into an annular ring channel surrounding the central melt channel. The method also comprises the step of injecting the second material from the annular ring channel into the central melt channel through a flow opening in the flow extension. In addition, the method comprises the steps of injecting a third material into an annular melt channel radially spaced from the central melt channel, and joining the third material from the annular melt channel with the first and second materials from the central melt channel.
The present invention also provides a method for injection molding of multi-layer products comprising the steps of injecting a first material and a second material into a central melt channel, and injecting the first material and the second material from the central melt channel into a cavity. In addition, the method comprises the steps of injecting a third material into an annular melt channel radially spaced from the central melt channel, and injecting the third material from the annular melt channel into the cavity.
Additionally, the present invention provides an article of injection molding comprising an outer layer and an inner layer made from a first material from an annular melt channel. The article also comprises a core layer between the outer and inner layers, and an intermediate layer between the inner layer and the core layer. The core layer is made from a second material from a central melt channel, and the intermediate layer is made from a third material from the central melt channel.